1. Field of the Invention
An aspect of the present invention relates to at least one of an image projecting device, an image processing device, an image projecting method, and a computer-readable recording medium.
2. Description of the Related Art
An image projecting device (a projector, etc.) is a device for projecting an image onto a projection object such as a screen. When an image is projected, a trapezoidal distortion may be caused on a projected image depending on a relationship between relative positions of an image projecting device and a projection object. Hence, an image projecting device may capture a projected image and correct a trapezoidal distortion of a projected image based on such a captured image.
Japanese Patent Application Publication No. 2010-028411 discloses a technique for projecting an image including characteristic points arrayed at equal spaces onto a projection surface, capturing an image of such a projection surface, calculating an amount of distortion (positional displacement) of a characteristic point, and correcting an image to be projected, depending on the calculated amount of distortion.
Japanese Patent Application Publication No. 2005-326247 discloses a technique for projecting a predetermined pattern image, sampling a planar area corresponding to a projection surface from a captured pattern image provided by capturing an image of the projection surface on a condition at that time, calculating a plane projection matrix from points on such a planar area, and calibrating an image to be projected based on such a plane projection matrix.
When interior illumination turns on (when light is incident on only an upper portion of a projection object) or when there is a local irregularity on a surface of a projection object, an image projecting device may project an image onto a projection object.
In any of techniques disclosed in Japanese Patent Application Publication No. 2010-028411 and Japanese Patent Application Publication No. 2005-326247, an image of a projection object on which an image is projected is captured and the captured image is binarized by using a constant threshold, whereby sampling of a characteristic point and sampling of a planar area are conducted. Accordingly, when a projection object is partially bright, or is partially dark due to an irregularity of a surface of the projection object, it may be possible to sample a characteristic point or a planar area.